Rolling-mill rolls are generally mounted in a rolling-mill stand or frame in respective bearings to the end of the rolls and are used for rolling billets, blooms or bars of metal in the hot or cold state to produce a variety of rolled products.
The displacement or change of mutual spacing of the rolls during the rolling operation is an inevitable phenomenon which depends on a number of factors.
Thus, while the two rolls may be held in position to define a predetermined gap between them by means at the bearing and even back-up rolls along the lengths of the rolling rolls, some degree of vertical displacement or change in the gap width can result in a dependence upon the physical properties and the geometry of the object which is rolled, the temperature at which the rolling is carried out, the conformation and composition of the roll, the play in the roll bearings, and elongation or other change of shape or dimensions of the rolling mill stand or frame. A relative offset in the horizontal direction will generally depend upon horizontal components of such play.
While the effect of a horizontal offset is not decisive for rolling flat objects such as strips, it is crucial in the rolling of shaped objects or profiles such as small bars, angles, rails, I-beams, H-beams and the like.
Indeed, even the slightest of horizontal offsets may be detrimental to the quality of rolled products of the latter type where geometry is important.
In practice, therefore, it has been found that the product quality depends to a considerable extend on preventing excessive offsets in both the vertical and horizontal directions and on preventing rolling by rolls which develop excentricities of the rolling surfaces.
It has already been proposed to provide means for measuring the spread of the rolls or the spread of the rolling surfaces of the rolls of a rolling mill, utilizing a discontinuance or periodic measurement approach and appropriate mechanical or optical means. Of course, should a defective operating state arise, this can only be observed after the system has been brought to standstill and an appropriate measurement taken.